Datasheet

3−2
Gain coefficients, entered via the I
2
C bus, must be entered as 32-bit binary numbers. The format of the 32-bit number
(4-byte or 8-digit hexadecimal number) is shown in Figure 3−3.
u
Coefficient
Digit 8
u u u S x x x
Coefficient
Digit 7
x. x x x
Coefficient
Digit 6
x x x x
Coefficient
Digit 5
x x x x
Coefficient
Digit 4
x x x x
Coefficient
Digit 3
x x x x
Coefficient
Digit 2
x x x x
Coefficient
Digit 1
Fraction
Digit 5
Sign
Bit
0
Fraction
Digit 6
Fraction
Digit 4
Fraction
Digit 3
Fraction
Digit 2
Fraction
Digit 1
Integer
Digit 1
u = unused or don’t care bits
Digit = hexadecimal digit
Figure 3−3. Alignment of 5.23 Coefficient in 32-Bit I
2
C Word
As Figure 3−3 shows, the hexadecimal value of the integer part of the gain coefficient cannot be concatenated with
the hexadecimal value of the fractional part of the gain coefficient to form the 32-bit I
2
C coefficient. The reason is that
the 28-bit coefficient contains 5 bits of integer, and thus the integer part of the coefficient occupies all of one
hexadecimal digit and the most-significant bit of the second hexadecimal digit. In the same way, the fractional part
occupies the lower 3 bits of the second hexadecimal digit, and then occupies the other five hexadecimal digits (with
the eighth digit being the zero-valued most-significant hexadecimal digit).
3.1.2 48-Bit 25.23 Number Format
All level adjustment and threshold coefficients are 48-bit coefficients using a 25.23 number format. Numbers
formatted as 25.23 numbers means that there are 25 bits to the left of the decimal point and 23 bits to the right of the
decimal point. This is shown in Figure 3−4.
2
−23
Bit
S_xxxx_xxxx_xxxx_xxxx_xxxx_xxxx.xxxx_xxxx_xxxx_xxxx_xxxx_xxx
2
0
Bit
2
16
Bit
2
22
Bit
Sign Bit
2
23
Bit
2
−1
Bit
2
−10
Bit
Figure 3−4. 25.23 Format